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04-21-2016 05:15 PM

Here's a strange question: I've seen presentations on the web that talk about RBEs being a specialized combination of MPCs between nodes.

Does anyone know of a reference that actually shows the MPC formulation for an RBE2? how about an RBE3?

3 REPLIES

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04-21-2016 05:50 PM

Dear Tony,

The NX NASTRAN **R-type** elements are elements that imposes fixed constraints between components of motion at the grid points or scalar points to which they are connected.** Thus, an R-type element is mathematically equivalent to one or more multipoint constraint equations**. Each constraint equation expresses one dependent degree of freedom as a linear function of the independent degrees of freedom.

Although sometimes the R-type elements are referred to collectively as rigid elements, the name “rigid” is misleading.** The R-type elements that are rigid consist of the RROD, RBAR, RBE1, RBE2, and RTRPLT**. **The RBE3 and RSPLINE are interpolation elements and aren’t rigid**. The RBE2 and RBE3 elements are the most commonly used R-type elements in the NX Nastran element library.

To learn more about **RBE2 vs. RBE3** you can visit my blog in the following address:

https://iberisa.wordpress.com/2015/10/13/rbe2-vs-rbe3-on-femap-with-nx-nastran/

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director

IBERISA • 48004 BILBAO (SPAIN)

WEB: http://www.iberisa.com

Blog Femap-NX Nastran: http://iberisa.wordpress.com/

IBERISA • 48004 BILBAO (SPAIN)

WEB: http://www.iberisa.com

Blog Femap-NX Nastran: http://iberisa.wordpress.com/

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04-22-2016 11:35 AM

I've seen the presentation you reference, and I generally understand the concepts of the RBEs. However, what I'm looking for are the actual MPC equations for the RBE2 and RBE3. Do you have anything that shows what those are?

Thanks,

Tony D.

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04-25-2016 12:26 PM

Try this link:

If the link doesn't work, just Google "rbe3 formulation"

It covers RBE3 formulation pretty well.

Joe

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